Use either no primer or a fired primer. As several have stated, live primer inerting can be iffy no matter what you do. Drilling holes in the case wall is OK, and provides positive ID. I have loaded numerous dummy rounds for use as museum displays and just left fired primers in place or replaced live primers with fired ones (I didn't drill holes in cases for those).

Military dummy action functioning rounds (.30-'06) made during WWII were loaded with potassium carbonate instead of propellant to simulate the weight and balance of a ball round. I had a few of those rounds once. I pulled a bullet and what was inside looked like fine white sand.